A. Relying on John v. Im, 263 Va. 315, 559 S.E.2d 694 (2002), the O'Rourkes argue that because neither Dr. Marvin nor Dr. Brown is a medical doctor, they were not "qualified to give expert testimony regarding causation of an injury that allegedly would result if [the child] did not have visitation with" Vuturo. In John, the Supreme Court of Virginia held that "[a]n opinion concerning the causation of a particular ` physical human injury is a component of a diagnosis, which is part of the practice of medicine."

Thus, we have repeatedly held that only a medical doctor is qualified to testify about the cause of a human physical injury. SeeId. at 602, 643 S.E.2d at 164-65; Conley, 273 Va. at 561, 643 S.E.2d at 134; Norfolk & W. Ry. Co. v. Keeling, 265 Va. 228, 235, 576 S.E.2d 452, 457 (2003); John v. Im, 263 Va. 315, 321, 559 S.E.2d 694, 697 (2002); Combs v. Norfolk & W. Ry. Co., 256 Va. 490, 496-97, 507 S.E.2d 355, 358-59 (1998). But seeVelazquez, 263 Va. at 104, 557 S.E.2d at 218-19 (allowing a sexual assault nurse examiner (" SANE" ) to express an opinion as to the cause of physical injuries in the context of a sexual assault).

Whether to permit a witness to qualify as an expert on a given subject matter is an issue submitted to the discretion of the trial court, and on appeal we will not reverse the trial court's ruling in this regard unless it plainly appears that the witness was not qualified. Atkins v. Commonwealth, 272 Va. 144, 153, 631 S.E.2d 93, 97 (2006); Johnson v. Commonwealth, 259 Va. 654, 679, 529 S.E.2d 769, 783 (2000). Notwithstanding these general principles regarding the qualification of an expert witness, Conley contends that we have established in Combs v. Norfolk Western Ry. Co., 256 Va. 490, 496-97, 507 S.E.2d 355, 358-59 (1998), and in John v. Im, 263 Va. 315, 321, 559 S.E.2d 694, 697 (2002), that only a medical doctor may give an expert opinion regarding the cause of a physical human injury. Upon this premise, Conley contends that because only a medical doctor may give an expert opinion regarding the cause of a human injury and "causation of a human injury is a component part of a diagnosis" as we stated in Combs, 256 Va. at 496, 507 S.E.2d at 358, then it necessarily follows that a non-physician may not also render an opinion regarding any medical diagnosis. Accordingly, Conley maintains that the trial court erred in qualifying Vanhoy as an expert in the diagnosis and treatment of PTSD and permitting her to give an expert opinion that the victim suffers with PTSD, regardless of any knowledge Vanhoy was shown to have gained by virtue of her training and experience in diagnosing PTSD as a licensed clinical social worker.

Before expert testimony may be admitted in a civil case to assist the fact finder, that testimony must meet certain requirements, including the requirement of an adequate factual foundation. Countryside Corp. v. Taylor, 263 Va. 549, 553, 561 S.E.2d 680, 682 (2002); John v. Im, 263 Va. 315, 319-20, 559 S.E.2d 694, 696 (2002); see Code §§ 8.01-401.1 and -401.3. Generally, the decision whether to admit expert testimony is a matter committed to the chancellor's sound discretion, and we will reject the chancellor's determination in this regard only when the record shows an abuse of that discretion. John, 263 Va. at 320, 559 S.E.2d at 696; Virginia Elec. Power Co. v. Dungee, 258 Va. 235, 258, 520 S.E.2d 164, 177 (1999). Expert testimony is inadmissible if it is speculative or based on assumptions that have an insufficient factual basis.

Hornsby stated that husband provided all his search parameters including price, square footage, and number of bedrooms and bathrooms. Citing John v. Im, 263 Va. 315, 559 S.E.2d 694 (2002), the circuit court declined to give any weight to Hornsby's testimony. The Supreme Court in John explained that “expert testimony generally is admissible if it will assist the trier of fact in understanding the evidence.”

The Virginia Supreme Court has not yet determined whether Virginia courts should employ the test for scientific evidence articulated by the United States Supreme Court in Daubert v. Merrell Dow Pharmaceuticals, Inc., 509 U.S. 579 (1993). See John v. Im, 263 Va. 315, 316, 559 S.E.2d 694, 697-98 (2002). Wide discretion must be vested in the trial court to determine, when unfamiliar scientific evidence is offered, whether the evidence is so inherently unreliable that a lay jury must be shielded from it, or whether it is of such character that the jury may safely be left to determine credibility for itself.

Id. Mohajer v. Commonwealth, 40 Va.App. 312, 320, 579 S.E.2d 359, 363 ( en banc) (2003); see also John v. Im, 263 Va. 315, 319-20, 559 S.E.2d 694, 696 (2002) (admissibility of expert testimony is submitted to the trial court's sound discretion upon application of fundamental principles, including the requirement that the evidence be based on an adequate foundation; we review trial court's ruling for an abuse of discretion). "The fact that a witness is an expert in one field does not make him an expert in another field, even though the two fields are closely related."

Because a licensed psychologist is not a medical doctor, a psychologist's opinion is not actually "medical" evidence. Cf. John v. Im, 263 Va. 315, 321, 559 S.E.2d 694, 697 (2002) (noting that an expert witness "was a licensed psychologist, not a medical doctor"). Said differently, although a psychologist may certainly be qualified to render an expert opinion, an expert opinion is not necessarily equivalent to a medical opinion.

Moreover, only a physician can offer expert testimony on causation under Virginia law. John v. Im, 263 Va. 315, 559 S.E.2d 694, 697 (2002). Dr. Inouye argues that Plaintiff cannot satisfy either of these expert requirements for her wrongful death claim because Plaintiff's only retained expert to testify on these issues, Dr. Hendricks, is not a psychiatrist who has a medical degree but rather a psychologist who does not.

Defendants submit that "it is generally understood that when an expert offers a medical causation opinion, the expert must have a medical degree or medical training." Defs.' Br. at 13 (citing Goodwin v. MTD Prods., Inc., 232 F.3d 600 (7th Cir. 2000); Estate of Harvey v. Roanoke City Sheriff's Office, 585 F. Supp. 2d 844 (W.D. Va. 2008); John v. Im, 559 S.E.2d 694, 697 (Va. 2002)). The Supreme Court of Virginia has held that an expert in biomechanical engineering who is not a medical doctor is not qualified to render an opinion on the cause of a plaintiff's back injury. Combs v. Norfolk and W. Ry. Co, 507 S.E.2d 355, 358-59 (1998).